Nothing specific happened. The Internet just evolves. New people interested in this kind of thing ended up spending more time on Facebook groups. Folks generally don't use forums any more. People got tired of answering the same old questions over and over. Lots of things have been covered to death, and anyway, this place was never as busy as somewhere like 8bc anyway for a variety of reasons and that ended up dying in some spectacular non spectacular fashion due to weird politics.
There is no good answer. There is no grand conspiracy. That's why nobody has answered you yet. It's just the way it goes.
p.s. HTML will never be allowed on forums like this for security reasons. It's a standard setup for all forum based software.